Chemical process



July 2 1946 A. D. GREEN I 2,403,276

` CHEMICAL PROCESVS I Filed April 2,1942

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Patented July 2, 1946 CHEMICAL PROCESS Arthur Donald Green, Cranford, N. J., asslgnor to Standard Oil Development Company, a corporation of Delaware Application April 2, 1942, Serial No. 437,305

Claims.

invention relates to improvements in the art of olefin production and. more particularly, it relates to a method of producing by catalytic dehydrogenation,l butadiene from butylene.

According to the present invention, I employ steam during the dehydrogenation of parafns, or oleflns such as butylenes, to form dioleflns, but in so doing I supply a substantial portion of the heat necessary to effect the dehydrogenation of the paraffin hydrocarbons or olefins by means of highly superheated steam. When butylene is dehydrogenated in externally heated tubes containing catalyst, and if the chemical heat of reaction must be transferred through the tube The present walls, then it is necessary to use rather small diameter tubes in order to fulfill the required conditions of short time of contact and a low temperature gradient. The use of such small tubes means that a very large number of them are required, which leads to an expensive reaction furnace. This is particularly serious in the case of the catalytic process. f

My invention will be best understood by reference to the accompanying drawing whereI have shown diagrammatically an apparatuslayout or flow sheet in which my invention may be carried into practical effect.

I shall nowdescribe my invention in detail by means of specific examples and in so doing shall refer to the accompanying drawing.

Referring therefore in detailto the drawing, I represents a line carrying steam from some source, which steam is vdischarged into a furnace 3 which may be a fixed coil type, a furnace or any other suitable heating device. The superheated steam is heated-to a temperature of from about 1800 F. to 2000 F. in heater 3, whereupon it is discharged into reactor 20 where it is mixed with preheated normal butylenes as will more fully appear hereinafter.

Meanwhile normal butylenes are introduced into the system through line 30, discharged into a. fresh feed and recycle storage vessel 32 from which they may be withdrawn through line 33 carrying a pump 35 and thence discharged into a furnace carrying a coil.38. The butylenes are heated in the furnace to a temperature of about say 1100 F. which is below their dehydrogenation temperature, and thereafter the preheated butylenes are discharged ,through line 40 into the reactor tube 20. The superheated steam and the preheated butylenes are, mixed in such proportions in reactor tube 20 as to give the mixture a temperature of about 1000 to 1400 F., preferregenerative 2 ab-ly from 1150"V to 1250 F., and the mixture is permitted to remainin the reactor tube fora very short period ofv time,V for example, for a period of time amounting toabout 0.01 to 0.1 second. In this reactor tube the total pressure is about 25 lbs/sq. in. absolute, and the partial pressure of the reactants is about 2 lbs./sq. in. absolute. The quantity of steam at the temperatures indicated fed to the reactor tube 20 is from about 7 to 12 mols'steam per mol of hydrocarbon.

In the reactor tube 20, the pressure may be subatmospheric, say of the order of 5 lbs/sq. in. absolute, or it may be as high as 40 lbs/sq. in.

absolute. i

In the dehydrogenation of butylenes, it is very essential to maintain a very short contact time in order to prevent undesired side reactions or decomposition products, and to this end, therefore, I pass them through the reaction at a sumcient space velocity to give the desired residence time. I then withdrawl the reaction products from reactor tube 20 through line 45, and imme; diately discharge quenching water from line 50 into line in order to lower thetemperature of the reactants, and thereafter I discharge the reactants into a cooler 5| where they ow'. upward against a downflowing spray of water dis,- charged into cooler through line 52.l The water serves to cool the reaction'products'below reaction temperature and also to Wash out tar which tar may be withdrawn vthrough line 55. The cooled and washed reaction products vare then withdrawn through line carrying a compressor 62 and discharged into a cooler 64 where a portion of the cooled and compressed gases are liquefied and discharged through line 66 into a receiver 68. The hydrocarbons liquefied in cooler 64 are withdrawn through line 10, thence discharged through line 12 into a receiving drum 15. The gaseoushydrocarbons are withdrawn fromreceiver 68 through line 80, then discharged into a refrigeration means Where they are sufliciently cooled to liquefy a major portion of the same, whereupon they are discharged.

through line into a separator 92. The liquefied hydrocarbons are withdrawn through line 94 and,`

discharged into line 12 for delivery to receiving drum 15. The tail gases consisting of hydrogen, methane, etc., are withdrawnr from separatorY 92 through line 98 and rejected from the's'ystem.

The material collected in receiving drum 15 is then stabilized and purified in thek following man-y ner: It is first withdrawnthrough4 line |00 ycarryinga pump |02 and thence discharged intol a stabilizer |06 carrying a heater |08, In stabilizer the heavy ends '(C5 and heavierhydrocarbons)V are withdrawn through line I Iwhile a C4 cut containingthe desired butadiene together with unreacted butylenesis withdrawn through line |20 and discharged into an extraction plant represented graphically by I22, where the C4 hydro# carbons are treated with a butadiene solvent.

Towers |06 and IIIIV are provided with the` usual re-lux means (not shown).l 'VVariousiso'lvents are n `suitable for this separation 'of butadiene Vfrom the -butylenes For example, I may use acetone,

methylamine, ammonia, aqueous cuprouschloride, ammoniacal cuprous acetate and others.Y I

prefer to employ the ammoniacal cuprous acetate in a liquid-liquid extraction process, i. e., to contactthe vC4 hydrocarbons inliquid phase with' the liquidammoniacal-'cuprous acetate. The cuprous acetatedissolves the butadiene,` andthis extract isrecoveredl through line I30'.- They butadiene product may be'recovered therefrom by distillationli known manner inapparatus not shown. Ihefbutylenes, on the other hand, are withdrawn through line M and recycled to storage drum 32 for processi-ng as previously indicated. vIpr'efe'r to employ catalysts suchas, for example, one having the following composition which is not affected by steam: l A f Parts byweight f'red'cmpos'ition as regardsthis catalyst', it is pointed out that the Mg'O may vary from .5D-95% that instead ofl using `copper oxide, I may use Y Z'rOfCrzOs; the oxides of manganese, coba1t,"ni`cl` el, thorium, zirconium, cerium, lead, bisiilth and aluminum. Of this latter group alumiiimioxide is' the best, with chromium oxide'ne'xt best.

To recapitulate, my present 'invention relates to improvements in the 'art of producing olefin, and preferably diolens such as butadiene from butylenes. It is generally known that the preparation of butadiene from butylenes is a highly sensitive reaction and difficult to control, particularly as to theV problem' ofvpreventing excessive cokeV formation and undesired side reactions. invention is directedv towards obviating both of these disadvantages of prior art methods in that I supply the superheat necessary for eiecting the desired dehydrogenation byl means of steam, 'and'mai'ntain short contact times, while utilizing a catalyst resistant to the effect of steam. In" other words, ,according to my process Irheat theV butylenes to' a temperature which Yis below dehydrogenation temperature and, thereafter discharge` them intoa reaction vessel where' they are admixed lwithV highly superheated lsteam also includes dehydrogenations involving crack-Y whereupon the butylenes are heatedY to reaction temperatures. I further maintain conditions so that the butylenes are in the reactor tube for a short period of time to prevent the undesired side reactions and are thereafter quenchced with some cooling fluid which may be oil, water, or even cold catalyst, in order to reduce the temperature of the, reaction products, topreserve the yields by preventing undesiredside reactions While I have 'emphasized'in the preceding description the production of butadiene from butyl- "enes, it will be understood that my invention is suiciently comprehensive to include dehydrogenation broadly kand therefore it includes such reaction asthe production of mono-olens from the corresponding aliphatic hydrocarbons, such as Ywhere butylene is produced frombutane. It

from butane.

What Iclaim is: c v

k1, A process 'for dehydrogenating bu-tylenes which comprises heating the butylene to a temperature below active'fdehydrogenation temperature, separately superheating steam, discharging the butylene and the steam into an otherwise substantially unheated reaction zone in such proportions that the Vbutylene -is heated to active dehydrogenation temperatures, passing the mixture of butylene and steam through said reaction zone in contactwithV a catalyst consisting essentially of a major proportion of magnesium oxide and minor proportions of iron oxide, copper oxing where, for example, propylene is produced ide, and potassium oxide permitting the-.butylene to remainV resident in the reaction Zone for a relatively short period of time, withdrawing reac- Vtion products from the reaction zone, rapidly cooling reaction products below reaction temperatures, separating butadiene fromthe other componentsof the reaction mass and recovering the said'butadiene.' Y Y 2. The method set forth in claim l in which the Y reaction Vproducts lremain resident -in Vthe :reac- 3. The method set'fertn in claim 1 in which butylene-is heated to a temperature inthe neighborhoo'd of v1,100 F. and the steam is heated to a temperature of from about 15800-10006 F, and in which the steam and thebutylene 'are' mixed in the 'reaction zonein a ratio of yfrom about 12 mols of steam per mol of hydrocarbon.- l

4. Process of dehydrogenating butylenes to produce butadiene, comprising preheating butylene to a i'emperature `somewhat below active dehy- 5. Process 'accordingl to claimV 4, in which the steam is heated tola temperature v c within the range of from abou'tLBOOrto 2,00'0 F. Y

v DONALD GREEN 

